Nowadays, innumerable processes used for filtering tobacco smoke are known. A great number of publications have been devoted to the additives of the smoke filters. These additives in the smoke filter are aimed to adsorb and/or absorb a certain ratio of the harmful components of cigarette smoke according to the eventual physical and/or physico-chemical relationships coming about between the constituents of the smoke filter and the components being present in the tobacco smoke.
A plethora of patented processes are particularly found under the collective noun of "substances binding and filtering out carcinogenic smoke components".
According to the published Japanese patent application No. 74/93600, the carcinogenic substance content of the tobacco smoke can be diminished by adding albumins of various types (such as lactalbumin or ovalbumin) to the smoke filter.
Various nitrogen oxides as toxic and irritating substances are found among the health-damaging materials detectable in the tobacco smoke. It has also been proven that nitrosated intermediates of nitrogen dioxide and other nitrogen oxides, such as N, N-dimethylnitrosamine, are particularly dangerous and carcinogenic to the human organism. Such substances are e.g. N'-nitroso-nornicotine or 4'-(methylnitrosamino)-1-(3-pyridyl)-1-butanone showing a high toxicity, carcinogenesis and mutagenesis [Carcinogenesis 6, 1543 (1985)]. A high number of papers have been published on the partial binding of nitrogen oxides.
In U.S. Pat. No. 3,407,820, manganese oxide and manganese dihydroxides are suggested for binding nitrogen oxides whereas the same purpose is aimed by using aluminum and zinc salts according to U.S. Pat. No. 3,875,949.
Heat-resistant resin compositions for removing by filtering the toxic tar content of the tobacco smoke are suggested in U.S. Pat. No. 3,294,095 wherein inter alia phenol-formaldehyde or urea-formaldehyde resins are used.
The research work aimed to bind cyanide compounds (HCN) in the tobacco smoke as well as to remove carbon monoxide (CO) is also described in the literature.
According to French patent No. 1,465,842, the carbonates and other salts of potassium and sodium make the smoke filter effective to bind hydrogen cyanide. According to U.S. Pat. No. 3,605,759, hydrogen cyanide is partially removed by adding polyoxyalkylene type substances to the smoke filter.
Polymeric additives are used in the smoke filter according to U.S. Pat. No. 3,311,115, which suggests zinc acetate and copper sulfate for increasing the filtration efficiency of the smoke filter. Hydrogen cyanide can effectively be bound by the said additives.
For binding carbon monoxide, the most various types of compouds, including native and macromolecular compounds, are listed in the literature. Carbon monoxide is absorbed e.g. by haemoglobin according to U.S. Pat. No. 3,982,897; whereas carbon monoxide is bound by manganese or palladium dihydroxyde as described in published Japanese patent application No. 82/136819.
A high number of literature references concern the binding of the health-damaging polycyclic aromatic compounds being present in the tobacco smoke.
According to U.S. Pat. No. 4,038,992, cellulose powder, starch and their derivatives as well as the dried concentrate of egg-white and inorganic mineral substances can effectively be used in the smoke filter as additives to filter out the polycyclic aromatic compounds being present in the tobacco smoke.
It can be stated from the literature that a high number of processes are worldwide known which suggest methods for the filtration of the tobacco smoke. It can also be stated that, in spite of the very high number of data concerning this subject, no conscious, conceptional method exists for the elimination and selective binding of the extremely harmful aldehydes, such as formaldehyde, released in the burning and being present in the tobacco smoke which, as it is commonly known, arises from a high-temperature burning.
A significant decrease in the formaldehyde content arising in the smoke on the burning of tobacco can be achieved by using the process according to the Hungarian patent No. 192,213 (equivalent to U.S. Pat. No. 4,753,250; Swiss patent No. 667,776; German (FRG) patent No. 3,532,618; or British patent No. 2,174,284), wherein the adsorptively not bound aldehydes, such as formaldehyde, are bound by enediol compounds going into a chemical reaction with the aldehydes.
According to a number of literature data, the toxic, carcinogenic, mutagenic and teratogenic effects of formaldehyde in the human organism are considered to have been proven. The above-cited Hungarian patent No. 192,213 gives an example, according to which the amount of the aldehydes arising in the smoke can be decreased by more than 50% when preferably 5 to 120%, depending on the filtration efficiency to be achieved, of an enediol type compound (e.g. reductone, dihydroxyfumaric acid, reductic acid, indanereductone, dihydroxymaleic acid, dehydro-L-ascorbic acid, L-ascorbic acid or their combinations), as calculated for one cigarette and based on the amount of the filling material, are added to activated carbon or of a mixture of activated carbon with an other granular adsorbent. A binding of 60% is described in the example.
It is suggested by this prior art that the formaldehyde being present in the smoke could be further decreased and nearly the 100% amount of formaldehyde could be eliminated by a further increase in the amount of the enediol compounds. However, the experiments carried out on the basis of this idea led to the unexpected result that the formaldehyde-binding capacity of the enediols was not significantly enhanced by a further significant increase in the amount of enediols and the highest value of the binding of formaldehyde amounted to 65%.
The aim of the present invention is to develop a filter for tobacco smoke, mainly for cigarette smoke, which is capable to bind completely or nearly completely not only the tar and other high-boiling health-damaging materials arising from the burning of tobacco but also the aldehydes being mechanically and adsorptively not bound, mainly the carcinogenic excited and ground-level formaldehydes in a chemosorptive way.
Our investigations led to the unexpected surprising result that reagents interacting with formaldehyde at a well-known high rate could not surpass the extent (65%) of binding formaldehyde described in Hungarian patent No. 192,213. These compounds were e.g. dimedone (5,5-dimethylcyclohexane-1,3-dione), a substance used for the analytical determination of formaldehyde [Spencer et al.: "The Kinetics and Mechanism of the Reaction of Formaldehyde with Dimedone", J. Am. Chem. Soc. 70, 1943 (1948)], as well as other commonly known compounds reacting at a high rate with formaldehyde in an addition reaction such as D, L-homocysteine, D,L-arginine, D,L-lysine as well as streptomycin consisting of streptose and streptidine bearing two guanidine groups (similarly to L-arginine) with a high reactivity toward formaldehyde.
An other compound, thiamine hydrochloride (vitamin B.sub.1) also contains an amino group with a high reactivity toward formaldehyde (similarly to L-lysine). The endoguanidine group of folic acid is also capable of reacting with formaldehyde at a high rate.
In spite of these facts, the highest value of 65% formaldehyde binding achieved by using the process described in the Hungarian patent specification No. 192,213 could not be surpassed by using the compounds listed hereinbefore in the filter.
Our systematic studies have shown that neither the compounds in themselves, which are similar to the enediols and possess a high nucleophilic additivity, nor their double, triple or quadruple systems in combinations were suitable to bind completely the 100% amount of formaldehyde being present in the smoke.